Method for manufacturing magnet wire

Abstract

A novel method for manufacturing magnet wire in a continuous process by which coatings of a flowable resin material may be applied concentrically to a moving elongated filament in thicknesses of about 16 mils or less. The filament can be a bare copper or aluminum conductor having round or rectangular configuration or an insulated conductor upon which a top or an intermediate coat of material is desirably applied. Coatings of one-half and one mil also can be applied by the method of the invention. By the method of the invention, magnet wire can be manufactured by continuously drawing the wire to size, annealing the wire, if necessary, insulating the wire with one or more coats of flowable resin material, curing the resin material, and spooling the wire for shipment, without interruption at speeds limited only by the filament pay-off and take-up devices used. The invention utilizes the flowable resin material to center the filament in a die, the size of the die controls the thickness of the coat to be applied. Only the resin material being applied to the filament is in contact with the filament. Thus, the mechanical wear normally associated with centering dies used in extrusion process and like devices is completely eliminated. Further, the method of the invention can be used to apply coats several times thinner than is possible with conventional extrusion apparatus and of materials different than those conventionally extruded onto filaments. In specific embodiments using heat softenable materials or melts, curing is no longer required; and thus, the need for curing, catalytic burners and the like as well as all concerns regarding atmospheric pollution are eliminated. The coated filaments and magnet wire made in accordance with the method of the invention have coatings which are surprisingly concentric and continuous when compared to magnet wire made by conventional methods.

What is claimed is: 
     
       1. A method of manufacturing magnet wire or the like in which a flowable but hardenable material is applied to an elongated filament to a desired thickness in a single pass whereby the filament may be drawn, or otherwise formed, coated and spooled in a continuous operation comprising the steps of: a. applying flowable material including less than about 5% weight solvent on said filament;   b. passing said filament through a stationary die at a speed of at least about 100 feet per minute, said die having a throat portion, an entrance opening larger than said throat portion interconnected by a converging interior wall thereby defining a die cavity between said throat portion and said opening and said filament and said wall, said filament in said throat portion and die cavity being spaced from said die;   c. at least partially filling said die cavity with said material at a temperature above the melting point thereof;   d. centering said filament in said throat portion solely with said material in said die cavity;   e. wiping the excess of said flowable material from said filament leaving an essentially concentric coat of said material on said filament of a thickness meeting the requirements of ANSI/NEMA Standards Publication No. MW1000-1977.   
     
     
       2. The method of claim 1 wherein said filling step comprises the steps of applying said flowable material to said filament in an amount of a slight excess, said filament carrying said flowable material into said cavity. 
     
     
       3. The method of claim 1 further comprising the step of hardening said material on said filament after said filament leaves said die. 
     
     
       4. The method of claim 3 wherein said hardened material is from about 1/2 mil to about 16 mils thick. 
     
     
       5. The method of claim 1 wherein said wiping step includes providing said die throat with an exit opening, said filament passing through said exit opening, said exit opening having a size relationship with the size of said filament controlling the thickness of the flowable material on said filament. 
     
     
       6. The method of claim 1 wherein said centering step includes the step of controlling the viscosity of said material within said die cavity. 
     
     
       7. The method of claim 1 wherein said flowable material is a heat softenable material, and said centering step includes the step of controlling the temperature of said die. 
     
     
       8. The method of claim 1 wherein said flowable material is a heat softenable material, and said centering step includes the step of controlling the temperature of said filament. 
     
     
       9. The method of claim 1 wherein said centering step includes the step of causing said material in said die cavity to form an annular support between said filament and said interior wall. 
     
     
       10. The method of claim 9 wherein said centering step includes the step of rotating said annular support of said material from said interior walls to said filament as said filament passes through said die. 
     
     
       11. The method of claim 10 wherein said causing step includes the step of controlling the viscosity of said flowable material within said die cavity. 
     
     
       12. The method of claim 11 wherein said filament is of the group consisting of bare copper and aluminum conductors, and insulated conductors having a base insulation previously applied. 
     
     
       13. The method of claim 11 wherein flowable material is of the group consisting of polyamides, polyethylene terephthalates, polyether imides, polyether ether ketones, polyesters, polycarbonates, polysulfones. 
     
     
       14. The method of claim 11 wherein said filament is from about 30 AWG gauge wire to about 3/8" rod. 
     
     
       15. A magnet wire or other coated elongated filament having an essentially concentric and continuous coating superimposed on said filament, wherein said coating is applied as a flowable material in accordance with the following steps: a. applying a flowable material including less than about 5% weight solvent on said filament;   b. passing said filament through a stationary die at a speed of at least about 100 feet per minute, said die having a throat portion, an entrance opening larger than said throat portion interconnected by a converging interior wall thereby defining a die cavity between said throat portion and said opening and said filament and said wall, said filament in said throat portion and die cavity being spaced from said die;   c. at least partially filling said die cavity with said material at a temperature above the melting point thereof;   d. centering said filament in said throat portion solely with said material in said die cavity;   e. wiping the excess of said flowable material from said filament leaving an essentially concentric coat of said material on said filament of a thickness meeting the requirements of ANSI/NEMA Standards Publication No. MW1000-1977.   
     
     
       16. The magnet wire of claim 15 wherein said filament is chosen from the group consisting of bare and prior coated copper and aluminum conductors. 
     
     
       17. The magnet wire of claim 15 wherein said filling step comprises the steps of applying said flowable material to said filament in an amount of a slight excess, said filament carrying said flowable material into said cavity. 
     
     
       18. The coated filament of claim 15 further comprising the step of hardening said material on said filament after said filament leaves said die. 
     
     
       19. The coated filament of claim 15 wherein said wiping step includes providing said die throat with an exit opening, said filament passing through said exit opening, said exit opening having a size relationship with the size of said filament controlling the thickness of the flowable material on said filament. 
     
     
       20. The coated filament of claim 15 wherein said centering step includes the step of controlling the viscosity of said material with said die cavity. 
     
     
       21. The coated filament of claim 15 wherein said flowable material is a heat softenable material, and said centering step includes the step of controlling the temperature of said die. 
     
     
       22. The coated filament of claim 15 wherein said flowable material is a heat softenable material, and said centering step includes the step of controlling the temperature of said filament. 
     
     
       23. The coated filament of claim 15 wherein said centering step includes the step of causing said flowable material in said die cavity to form an annular support between said filament and said interior wall. 
     
     
       24. The coated filament of claim 23 wherein said centering step includes the step of rotating said annular support of said flowable material from said interior walls to said filament as said filament passes through said die. 
     
     
       25. The magnet wire of claim 15 wherein said filament is of the group consisting of bare copper and aluminum conductors and insulated conductors having a base insulation previously applied, said material is of the group consisting of polyamides, polyethylene terephthalates, polyesters, polycarbonates, polysulfones, polyether imides, polyether ether ketone, and epoxys, said conductors are from about 30 AWG gauge wire to about 3/8" rod, said hardened material is from about 1/2 mil to about 16 mils thick.